Fast availability simulation

The Availability of a system, device or component in an operational cycle, defined by normal operation—malfunction (failure) — wait — repair, is considered and defined in the form of a random variable. By the use of the fast convolution techniques originally developed for structural reliability applications, the cumulative distribution function of this random variable is obtained together with its mean (equivalent to the long run Average Availability) and standard deviation. The technique described includes preventive maintenance, may be used with any assumed probability distributions of failure, waiting, repair and preventive maintenance times, and may take account of correlation between these parameters. The results are equivalent to those which may be obtained by conventional numerical simulation of repair cycles, but the procedure described is likely to be faster and more economical of computing time and amenable to use on microcomputers.